1. Field of the Invention
The present invention relates to a sound source integrated circuit including an effect adding device and a sound source apparatus using the sound source integrated circuit, which are employed in an electronic musical instrument for generating musical tones.
2. Description of the Related Art
A recent remarkable development of LSI techniques has brought integrated circuits, which include various functions within one chip. A sound source LSI, for example, of an electronic musical instrument includes a digital signal processor (DSP) for adding effects onto a sound signal. As a result, an electronic system, which employs an effector of a high performance for adding reverberation and other like effects on a sound signal, has been available at a low price.
FIG. 1 is a view illustrating a whole structure of a conventional electronic keyboard instrument with a chip of a sound source LSI equipped therein. In FIG. 1, a central processing unit (CPU) 1803 scans operating states of a keyboard 1801 and a switch unit 1802. Based on the result of the scanning operation, the CPU 1803 controls generation of sounds of a sound source LSI 1804. The sound source LSI 1804 generates a musical tone signal in accordance with instructions supplied from the CPU 1803, and performs an effecting process on the musical tone signal, using a random access memory (RAM) 1805 as a time delay memory. The resultant digital musical tone signal is further supplied to a D/A convertor 1806. The D/A convertor 1806 converts the supplied digital musical tone signal into an analog musical tone signal, which is audibly output through an amplifier 1806 and a speaker 1808.
FIG. 2 is a view illustrating a whole structure of other conventional electronic keyboard instrument of high quality, which employs two chips of sound source LSIs to be distinguished from widely used instruments in tone color and the number of polyphonic tones.
The electronic keyboard instrument of FIG. 2 is different from the instrument of FIG. 1 merely in that musical tone signals are generated by two sound source LSIs 1904, 1905 instead of a single sound source LSI, and are subjected to the effect process. With respect to other points, the electronic keyboard instrument of FIG. 2 operates in a similar manner to the instrument of FIG. 1. The musical tone signals are subjected to the effect process and D/A conversion. Two musical tone signals output from D/A convertors 1907, 1909 are sent to an amplifier 1910, where these signals are mixed together, and audibly output through a speaker 1911.
FIG. 3 is a view illustrating a whole structure of the other conventional electronic keyboard instrument of high quality, which employs two chips of sound source LSIs to be distinguished from widely used instruments in tone color and the number of polyphonic tones.
In FIG. 3, a CPU 21101 scans operating states of a keyboard 21101, switch unit 21102, and controls generation of sounds by sound source LSIs 21104, 21105 based on the result of the scanning operation. The sound source LSIs 21104, 21105 generate musical tone signals in accordance with instruction supplied from the CPU 21103, and supplies the musical tone signals to a DSP 21106 for effecting process. A DSP which is superior in performance than that used in the sound source LSI 1004 of FIG. 1 is used as the DSP 21106.
The DSP 21106 performs an effect process on the musical tone signals transferred from the sound source LSIs 21104, 21105, using a RAM 21107 for a time delay process. The resultant digital musical tone signal is converted into an analog signal by a D/A convertor 21108, and then audibly output through an amplifier 21109 and a speaker 21110.
As described above, when a plurality of chips of sound source LSIs are used, each of the plural chips of sound source LSIs performs an effect process independently of each other, so that each of the plural chips of sound source LSIs needs its own components such as a RAM for a time delay process and a D/A convertors for the DSP of the respective sound source LSI for performing an effect process. As a result, usage of a large number of chips of sound source LSIs in an electronic system invites such various problems as make the system large in size, and raise manufacturing costs.
Furthermore, usage of a large number of chips of sound source LSIs in an electronic system of a high grade needs expensive DSPs, of high performance, specialized for executing effect processes of high quality, resulting in a large sized system and increased manufacturing costs.